I have been told that getting an FAA field approval is a lot like getting an elephant pregnant. 1. It's harder work than anyone would imagine, 2. It's accomplished by a lot of screaming and yelling, 3. Both parties are not sure of what the other is doing, and 4. It takes 19 months before you see any results. Well, this tongue-in-cheek metaphor may not be a 100 percent right, but it is not a 100 percent wrong either. Let's examine the policy behind field approvals and hopefully shine a little light on this murky subject.
What is a field approval?
A field approval is the granting by an FAA airworthiness safety inspector of an FAA approval for a major repair or major alteration based on examination of data or physical inspection or testing. There are three kinds of field approvals for which the local FAA inspector can sign off in Block 3 of the FAA Form 337. They are:
Examination of Data only: This is the most common form of field approval. The mechanic and repairman submit "acceptable" data to the local FAA office for approval. Once the data is approved in Block 3, the mechanic can make the major repair or alteration and have it signed off by an IA, repair station, or air carrier. Many mechanics make the mistake that once this data is field approved, it can be used over and over again to make another identical major repair or major alteration. This is not so! This field approval based on "Examination of Data only" is only for the aircraft identified in Block 1 of the FAA Form 337. However, if you want to do the exact same repair or alteration to another like make or model aircraft, you can use the original FAA Form 337 as the basis (acceptable data) for obtaining a new field approval for the second aircraft.
Physical Inspection, demonstration or testing of the repair or alteration: This is not done very often, but it does come in handy when a mechanic finds the wrong engine in the aircraft or when an auto pilot is on the aircraft and operating for several years but there is no paperwork. Since the aircraft has flown successfully for many hours, an FAA inspector can, if satisfied with the installation, approve the installation. The inspector would then sign Block 3 of a new FAA Form 337 that describes the engine or component and its installation.
Examination of data only for duplication on identical make and model aircraft by the original modifier: This is a procedure that saves the mechanic and the FAA a lot of time. For example, if a mechanic wants to install duplicate GPS on a Cessna 152 or vacuum storage containers for Jalapeno peppers on a Beech 18, he can do it with just one field approval. All the mechanic has to do is submit the acceptable data for the alteration or repair and ask the FAA inspector to sign Block 3 of the FAA Form 337 along with the statement that approves duplication of this repair/alteration on identical make and model aircraft by the original modifier. How does this work?
When the technician finishes a duplicate alteration on the next aircraft, he sends the FAA a regular FAA Form 337 properly identifying the second aircraft and identifying the approved data (date/aircraft) obtained under field approval on Block 8 of the Form 337. To avoid a phone call from the Flight Standards District Office (FSDO), I would recommend that you attach a duplicate copy of the original Field Approval Form 337.
One must understand that this field approval for duplication is not a property right like an STC is. The original modifier cannot "sell" the field approval to another party or "rent out" the data to another person.
Why do you need a field approval?
The question should be, why do you need approved data? In order to perform a major repair or a major alteration, four regulations require that you do the work in accordance with approved data. The regulations are FAR sections 65.95, 121.378, 135.437, and 145.51.
Approved data can be: type certificate data sheets (TCDS), supplemental type certificates, (STC), airworthiness directives (AD), airframe/engine/propeller FAA-approved instructions, appliance manufacturer's manuals or instructions (even if they do not specifically state they are FAA approved), CAA Form 337 dated prior to 10/1/55, FAA Form 337 field approved for multiple installation in Block 3, technical standard order (TSO), DER-approved data, designated alteration station (DAS), designated option authorization-approved data, repair data performed under a SFAR 36 for the holder's facility only, parts manufacturer approval, and anything stamped "FAA Approved Data." If you cannot find the approved data to make the repair or alteration from the list above, the next step would be to apply for an STC or a field approval.
Not a field approval
Field approvals are not covered under a regulation. The field approval process is covered under FAA policy in FAA Order 8300.10 Volume 2 Chapter 1. Because the field approval is a procedure, dictated by policy and not a rule, the mechanic is not automatically entitled to a field approval - even if the mechanic submits a "perfect" FAA Form 337 to the FAA. And why not? Because the authority to grant a field approval and the great burden of responsibility that goes with signing Block 3 of the FAA Form 337 has been delegated only to the local FAA FSDO airworthiness inspectors.
FAA inspector's responsibility
Before granting a field approval, the FAA inspector must determine that the affected aircraft or component part can be expected to operate safely and conform to the regulatory requirements by which the aircraft or part was certificated under.
The responsibility for data approval is so monumental that no one, not even the FAA administrator, may force the inspector to approve or deny a field approval for major repair or major alteration against the inspector's better judgment. The inspector's judgment is based on his or her level of knowledge, skills, experience, and background in the aircraft or component in which the major repair or alteration is going to be performed.
For example, if the inspector has no experience with installing fuel tanks for rocket fuel in hot air balloons, then he or she should deny the request. This does not mean the mechanic is left out in the cold. He is welcome to find another inspector in the same office or another inspector in another FAA office with the experience and background to sign off Block 3.
Since it's the inspector who makes the final decision and is held accountable by the FAA for that decision, most inspectors are overly cautious when it comes to signing off a field approval. Wouldn't you be? Have you ever worked along side any mechanic during your aviation career that you would not sign off anything he did? Yet, mechanics routinely submit requests for field approval to FAA inspectors who barely know them let alone worked along side of. This makes inspectors a little nervous when their career is on the line.
When I taught FAA inspectors the major repairs and major alteration course at the FAA Academy, and when I wanted to emphasize the importance of this approval and the need to do it right, I said this to my students: "When you sign Block 3 of the FAA Form 337 you cease being a judge and become a partner in the major repair or alteration being performed."
Another thing mechanics should consider is that the FAA inspector does not get "points" for each Block 3 the inspector signs. Field approvals are listed as demand work in the inspectors work program. The inspector is graded on his or her performance on required items such as Part 145 inspections or surveillance of Part 121 or 135 operators.
So the next time the FAA inspector signs a Block 3 for you, don't forget to thank your partner who signed his life away, just like you did on the bottom of the Form 337.
What cannot be field approved?
Some major alterations are so complex that it would take a whole team of engineers to put their arms around it. So the policy folks in Washington put forth a list of major alterations that require engineering approval or even an application for an STC in FAA Order 8300.10. The following is a partial list of items that cannot be field approved.
1. Increases in gross weight or major changes to center of gravity range.
2. Installation or relocation of equipment that may adversely affect structural integrity or flight or ground handling characteristics of the aircraft.
3. Any alteration of the control surfaces' dimensions, travel, or balance.
4. Changes to the aircraft's basic dimensions or external configuration.
5. Changes to landing gear.
6. Changes to manifolding or engine cowling that would affect the amount or direction of cooling air.
7. Changes to primary structures that may adversely affect strength or produce flutter or vibration.
8. Changes to exterior fuel systems or vents.
9. Changes to the basic engine or propeller design, primary controls, or operating limitations.
10. Changes in fixed fire extinguisher or detector system.
11. Modifications to TSO radio communications and navigational equipment.
You are finishing up the industrial strength hair dryer installation for the boss's wife in back of your company's Lear Jet. When you test the dryer unit, it fails spectacularly. You order parts AOG, but the boss wants to go to Pittsburgh tomorrow. What do you do? Answer: The aircraft may be released for service with an incomplete installation if the following has been accomplished.
1. The alteration data you are using to make the installation has been FAA-approved.
2. The incomplete alteration has been determined not to affect the safe operation of the aircraft.
3. The equipment installed remains deactivated (circuit breakers collared) and has placards affixed on or near to it stating the unit is not to be used.
4. The weight and balance report reflects the incomplete installation.
5. The maintenance records have been completed and signed off for the work that was actually completed.
6. The operator should be advised that the alteration is incomplete and may be subject to a conformity inspection when the entire project is completed.
How to sign off work when a flight test is required
Some STCs and field approvals may require an operational flight test of the equipment or alteration installed in accordance with Section 91.407. The mechanic must sign off all the work performed on the FAA Form 337 and maintenance records in accordance with Section 43.9. Then, someone with a minimum rating of a private pilot, appropriately rated in the aircraft, flies and makes the operational checks on the equipment installed and logs the "return to service" statement in the maintenance records.
Helpful hints for getting a field approval
1. Do not cut metal, splice wire, or install equipment until you receive the field approval. The only thing worse than not getting a field approval is telling your customer the expensive equipment that you installed in his aircraft has to be removed.
2. Determine if the repair or alteration is major as defined by FAR 1. If the work is considered major, go to the next step.
3. Do not set unreasonable goals for getting the field approval signed. Thirty days is reasonable for the FAA, but maybe not so reasonable for a mechanic who has a payroll to meet or bills to pay. Remember that a field approval is a lot cheaper than getting an STC and a lot quicker, too.
4. Research all sources for approved data to make the repair or alteration. If the alteration is already listed on the aircraft's type certificate data sheet, then the alteration is already approved and should be signed off as a minor alteration in the aircraft's maintenance logbooks.
5. Call or visit the FAA inspector ahead of time. Describe your repair or alteration. Find out what kind of data the inspector wants to see to increase his comfort zone. Then, assemble the data in a reasonable and understandable format. The data submitted must be accurate, current, and support as well as describe the alteration or repair. Data can be in the form of drawings, sketches, or photographs. Reference to AC 43.13-1a and 2a, manufacturer's maintenance manuals, kits, bulletins, and service letters may be helpful.
6. A cover letter describing in detail the field approval and how you are going to accomplish the repair or alteration is not required but it shows a touch of professionalism, which in turn raises the level of trust the inspector has in his or her new partner.
7. Avoid submitting a sloppy written or dirty Form 337 for a field approval. It dramatically lowers the level of trust between the mechanic and FAA inspector. When I worked in a field office, a mechanic submitted a Form 337, equipped with finger prints and a coffee cup ring. I denied it and sent it back to him with my coffee cup ring.
8. When your research is done, send the FAA inspector duplicate copies of the Form 337 along with the data you want approved. If the inspector does not sign Block 3, find out what the inspector did not like and try again.